Curiosmos
  • Home
  • Unsolved Mysteries
  • Ancient Civilizations
  • Cosmic Phenomena
  • Alien Theories
  • Curious Lists
No Result
View All Result
Like us on Facebook
Curiosmos
  • Home
  • Unsolved Mysteries
  • Ancient Civilizations
  • Cosmic Phenomena
  • Alien Theories
  • Curious Lists
No Result
View All Result
Curiosmos
No Result
View All Result

Sahara climate cycle reveals desert turns green every 20000 years

"The story of North African climate is dominantly this 20,000-year beat, going back and forth between a green and dry Sahara..."

Ivan PetricevicbyIvan Petricevic
January 7, 2019 - Updated on April 17, 2025
in Editor's Picks
Share on FacebookShare on Twitter

The Sahara climate cycle isn’t just a theory — it’s a pattern written into the Earth itself. Roughly every 20,000 years, the world’s largest desert shifts gears, transforming from a sun-blasted wasteland into a green, living landscape. Now, new research from MIT confirms what geologists have suspected for decades: these dramatic swings are triggered not by random chance or distant ice ages, but by the slow, predictable tilt of Earth’s axis.

A desert on a timer

Illustration of the Sahara climate cycle showing the desert transitioning from arid sand dunes to a lush green savanna due to Earth’s axial tilt. Credit: Curiosmos.
Illustration of the Sahara climate cycle showing the desert transitioning from arid sand dunes to a lush green savanna due to Earth’s axial tilt. Credit: Curiosmos.

The Sahara climate cycle is driven by changes in Earth’s axial tilt, which affects how much summer sunlight reaches the Northern Hemisphere. Every 20,000 years or so, the tilt shifts just enough to dramatically boost seasonal sunlight over North Africa. When that happens, the region’s monsoon season strengthens, bringing rain to a landscape that today looks almost uninhabitable.

During these wet periods, the Sahara turns green. Vegetation spreads. Lakes fill. Wildlife flourishes. And crucially, it becomes a possible migration route for early humans.

But when the tilt swings back — lowering summer sunlight — monsoons weaken. The rains disappear, and the Sahara dries out again.

Related Posts

Geographical location and typical habitat of the Welwitschia plant. Credit: Tao Wan

10 Things You Need to Know About the “Immortal” Welwitschia Plant

August 21, 2021 - Updated on January 14, 2025
A view down the the borehole at about 3,500 feet (1,070 meters) below the ice. Image Credit: Kathy Kasic/salsa-antarctica.org.

Ancient life beneath Antarctica raises new questions about survival in extreme worlds

January 16, 2019 - Updated on April 17, 2025

According to MIT professor David McGee, who led the study, “The story of North African climate is dominantly this 20,000-year beat, going back and forth between a green and dry Sahara.”

The dust that tells the story

To track the Sahara climate cycle, scientists analyzed deep-sea sediment cores collected off the coast of West Africa. Every year, millions of tons of Saharan dust are blown westward by dry northeasterly winds and settle on the ocean floor.

These layers of dust act like a natural climate logbook. Thick, dusty layers indicate dry periods. Thin, less dusty layers point to greener, wetter times.

But dust alone isn’t enough. To determine how fast that dust accumulated — and how reliable the timeline really is — the researchers turned to a rare element: thorium-232. This isotope is produced at a constant rate in seawater and quickly sticks to sinking sediment. By measuring thorium in the cores, the team could calculate the pace of sediment build-up and create an accurate chronology stretching back 240,000 years.

Rethinking old assumptions

Until now, many scientists thought the Sahara’s wet-dry cycle followed Earth’s 100,000-year ice age rhythm. But the new data didn’t match that pattern. Instead, it aligned almost perfectly with the 20,000-year tilt cycle.

“We’ve assumed that ice ages have been the key thing in making the Sahara dry versus wet,” McGee said. “Now we show that it’s primarily these cyclic changes in Earth’s orbit.”

That means the Sahara has switched between desert and grassland not once or twice, but dozens of times in just the past quarter million years.

Understanding the Sahara climate cycle could reshape how we study early human migration. During wet phases, the Sahara wasn’t a barrier — it was a corridor. Rivers and lakes made it passable, even inviting.

That opens the possibility that waves of human movement out of sub-Saharan Africa may have timed with these green periods. Researchers are now looking at archaeological sites and DNA evidence to see if there’s a link between migration pulses and Sahara greening events.

In short, when the desert disappeared, people moved — and those migrations may have helped shape entire civilizations.

The MIT team’s findings offer just a glimpse into a much larger climate puzzle. More sediment cores from other parts of the ocean — and even from within the Sahara itself — could stretch the timeline further back, or reveal new patterns entirely.

For now, one thing is clear: the Sahara has never been static. It’s not a frozen landscape in time — it’s dynamic, cycling between extremes, shaped by forces we’re only just beginning to understand. And if the Sahara climate cycle continues its natural beat, it will one day turn green again.

Share373Tweet98Share27ShareSend
Ivan Petricevic

Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

Related Posts

An image of ring of dust around planet. Image Credit: International Gemini Observatory, NOIRLab, NSF, AURA and Tom Esposito, UC Berkeley.
Editor's Picks

Scientists Baffled by 4 Mysterious Objects in Deep Space that are Unlike Anything Ever Observed

July 9, 2020 - Updated on January 21, 2024
The James Webb Space Telescope has found a galactic question mark
Editor's Picks

How Did Our Universe Begin?

December 20, 2024
The Eye of the Sahara Atlantis theory claims a forgotten civilization lies hidden beneath African sands
Editor's Picks

The Eye of the Sahara Atlantis theory claims a forgotten civilization lies hidden beneath African sands

March 1, 2019 - Updated on April 18, 2025
Here Are 5 of the Most Bizarre Elongated Skulls Ever Found
Editor's Picks

Here Are 5 of the Most Bizarre Elongated Skulls Ever Found

May 18, 2019 - Updated on May 2, 2023
An illustration of an advanced alien civilization species.
Editor's Picks

Former Tesla AI Expert Says Alien Civilizations are “Everywhere”

November 26, 2022 - Updated on January 20, 2024
The Al Naslaa rock formation stands as one of Earth’s most extraordinary geological marvels
Editor's Picks

The Al Naslaa rock formation stands as one of Earth’s most extraordinary geological marvels

August 31, 2024
  • About
  • Privacy Policy
  • Fair Use Notice
  • DMCA / Removal
  • Impressum
  • Contact
  • Fact-Checking Policy
  • Ethics Policy
  • Ownership and Funding Information
  • Impressum
CURIOSMOS.COM

Welcome Back!

Login to your account below

Forgotten Password?

Retrieve your password

Please enter your username or email address to reset your password.

Log In
No Result
View All Result
  • Home
  • Unsolved Mysteries
  • Ancient Civilizations
  • Cosmic Phenomena
  • Alien Theories
  • Curious Lists